The purpose of this study is to measure the mechanism of ocular hypotension of the structurally modified prostanoid AGN 192024. 25 normal human volunteers between the ages of 21 and 48 underwent a randomized, double-masked, placebo-controlled study in which intraocular pressure, aqueous humor flow, and tonographic resistance to outflow were studied. Measurements of aqueous flow were made during the day and during the night while subjects slept. Intraocular pressure was measured with the Goldmann tonometer, and resistance to outflow was measured by electronic recording Schiotz tonography.